“…Therefore, EEG has been widely used in the study of neural mechanisms and clinical diagnosis of mental diseases [e.g., depression ( Feng et al, 2012 ; Jesulola et al, 2015 ; Steiger and Pawlowski, 2019 ), anxiety disorder ( Tyrer and Baldwin, 2006 ; Olatunji et al, 2010 ; Hilbert et al, 2014 ), sleep disorder ( Papadimitriou et al, 1988 ; Huang et al, 2019 ), and epilepsy ( Mporas et al, 2015 )]. Common EEG analysis methods include power spectral density (PSD) analysis ( Fenton et al, 1980 ; Pradhan and Dutt, 1994 ) [e.g., absolute power (AP), relative power, and power ratio], non-linear dynamics analysis ( Nikias and Petropulu, 1993 ; Alotaibi et al, 2022 ) [e.g., approximate entropy, fuzzy entropy (FE), and sample entropy], and brain functional connectivity (FC) analysis ( Stam et al, 2007 ; Piho and Tjahjadi, 2020 ; Li et al, 2022 ) [e.g., Partial directed coherence (PDC), mutual information (MI), and phase-lag-index (PLI)]. In this study, the PSD, FE, and PLI were used as the main methods to analyze EEG data and to reveal the electrophysiological differences of GAD in different age groups.…”